32. THE NUCLEIC ACIDS OF MICROORGANISMS 



173 



TABLE V 

 DNA Composition of Mycobacteria and Actinomycetes 



References 

 ■ J. D. Smith and G. R. Wyatt, Biochem. J. 49, 144 (1951). 

 6 S. G. Laland et al., J. Chem. Soc. p. 3224 (1952). 

 A. S. Spirin et al., Biokhimiya 22, 744 (1957). 



d T. Tsumita and E. Chargaff, Biochim. et Biophys. Acta 29, 568 (1958). 

 e E. Vischer et al., J. Biol. Chem. 177, 429 (1949). 

 ! A. S. Jones el al., J. Chem. Soc. p. 2454 (1957). 

 o A. N. Belozersky et al., Doklady Acad. Nauk S.S.S.R. 119, 330 (1958). 



position from that of the true actinomycetes. This is in accord with the fact 

 that the actinomycetes and acid-resistant mycobacteria represent two dif- 

 ferent, rather isolated groups of the order Actinomycetales. However, the 

 low value of the (A + T)/(G + C) ratio in mycobacteria may testify to 

 their relationship with the Actinomycetales. 



As to the true actinomycetes (the families of Actinomycetaceae and 

 Streptomycetaceae), all analyzed representatives, being characterized by 

 an extreme GC-type of DNA, show a rather considerable similarity in 

 their DNA composition. 147 It seems that we may regard them as rather 

 closely related organisms forming one peculiar group which is perhaps 

 narrow in systematical aspect. All four representatives of the genus Strepto- 

 myces studied are statistically absolutely indistinguishable by their DNA 

 composition. 147 Thus, in the case studied, no species specificity of DNA 

 composition was found in the species within a genus. At the same time, 

 there can be found some differences in the DNA composition of different 

 actinomycete genera. 



The data on the DNA composition of fungi are presented in Table VI. 

 Unfortunately, there exist only few data on this group of microorganisms, 



